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    SubjectRe: SATA kernel-buffered read VERY slow (not raid, Promise TX300 card); 2.6.23.1(vanilla)
    Linda Walsh wrote:
    > Alan Cox wrote:
    >>> rate began falling; at 128k block-reads-at-a-time or larger, it drops
    >>> below
    >>> 20MB/s (only on buffered SATA).
    >>
    >> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
    >> readahead' flaw.
    > ---
    > I'm not aware, off hand, how to disable NCQ. I haven't had any
    > NCQ- or SATA- capable disks before a few weeks ago.

    See here:

    http://linux-ata.org/faq.html#ncq

    >
    >>> The only way I could tell before was using hdparm to read the
    >>> parameters. Since that doesn't work, it's hard to tell if they
    >>> are set correctly...
    >>
    >> hdparm supports identify to read modes on drives with libata. The one
    >> thing you cannot do is force modes right now.
    >>
    >>> More importantly, how does one set parameters for acoustic and power
    >>> saving parameters? Some of my disks are used as 'backup' devices for my
    >>
    >> hdparm or blktool
    > ----
    >
    > I have hdparm-v7.7. There are some areas where it shows information,
    > but areas where it
    > does not work jump out and lead me to suspect whether or not areas
    > that don't give explicit "ERROR" messages are presenting valid info.
    >
    > Problem areas (using hdparm, disk=Seagate Barracuda 16MB cache, model=
    > ST3750640AS):
    > 1) The drives current 'multicount' setting isn't readable or settable.
    > param "-i" shows "?16?" (with question marks around 16) and "-I" simply
    > shows "?" for the current setting. Attempting to <read|set> it:
    > "HDIO_<GET|SET>_MULTCOUNT failed: Inappropriate ioctl for device"

    I don't think you can get or get the multi count currently, it just uses
    the best supported value.

    > 2) Drive Advanced Power Management setting("-B") (write-only):
    > "HDIO_DRIVE_CMD failed: Input/output error"
    > 3) Drive Acoustic ("-M"), read = " acoustic = not supported",
    > write = " HDIO_DRIVE_CMD:ACOUSTIC failed: Input/output error"
    > Note: drive detailed info from "-I" says:
    > "Recommended acoustic management value: 254, current value: 0"
    > (i.e. - there seems to be no way to set recommended value)

    Not sure about these ones.. Does anything show up in dmesg when you do this?

    > 4) 32-bit IO setting ("-c") (don't know if this important given the disk's
    > raw-read speed, it may be meaningless for SATA)
    > "IO_support = 0 (default 16-bit)"*
    > *

    This setting is not meaningful for anything using DMA.

    > FWIW -- the spindown/standby timeout ("S") does seem to work.
    >
    >>> other computers. With the ATA disks, they were kept "spun down" when
    >>> not
    >>> being used (only used, 'normally', in early AM hours).
    >>
    >> Well for backup devices you can use the fact SATA is hot/warm plug.
    > ---
    > I don't follow. It is an internal drive. Are their software "logically
    > unplug" commands that automatically re-"plug-in" the drive on access
    > and spin it back up like the spindown/standby timeout does? Or were
    > you referring to SATA's general hot/warm plug ability (if my hardware
    > setup, drive-slots, etc, permitted removability)?

    I think they were referring to physically hotplugging the drive. This is
    more practical if you have a removable drive caddy, or if the drive is
    hooked up through eSATA.

    --
    Robert Hancock Saskatoon, SK, Canada
    To email, remove "nospam" from hancockr@nospamshaw.ca
    Home Page: http://www.roberthancock.com/



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